Adenosine triphosphate (ATP), which is the major energy source for heart muscle contraction and active ion transport, is synthesized mainly by respiratory chain linked oxidative phosphorylation. The objective of this research is to deduce the detailed mechanism for oxidative phosphorylation. The transport of electrons to oxygen through the respiratory chain is coupled with the synthesis of ATP. The hypothesis is that a chemically identifiable high energy intermediate is formed in the primary energy conserving process. An electron deficient sulfide may be formed and subsequently converted to the presumed high energy phosphorylating intermediate, a phosphorylated sulfonium salt. A series of physical organic, electrochemical, and spectroscopic techniques will be used to investigate this high energy intermediate. Electrochemical methods appear to be the most suitable for generating highly reactive intermediates free from contaminants. The structures of the intermediates will be determined spectroscopically (ir, uv, and esr). The techniques of physical organic chemistry will be used to study the reactions of these intermediates.